Author Topic: Working Of SSHD:--------  (Read 556 times)

shajahan

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Working Of SSHD:--------
« on: December 20, 2014, 04:30:53 AM »
An SSD can read and write data many times faster than the best mechanical hard drive. On the downside, flash memory is many times more expensive than the innards of a typical hard drive, so manufacturers have limited their SSD capacities to hit reasonable price points: A 128GB SSD costs about $130, and for that same price tag, you can buy a 3.5-inch desktop hard drive that delivers 2TB of storage, or a 2.5-inch laptop drive that provides 1TB of storage.

Two years ago, Seagate (quickly followed by Samsung) introduced a drive that married a small SSD with a mechanical drive. The objective was to deliver the superior speed of an expensive SSD, while retaining the higher capacity and lower cost of a conventional hard drive. Now that Toshiba and Western Digital are joining the party, it's a great time to explain in more detail what hybrid drives are and how they operate.

Hybrid drives work much in the same way as the current dual-technology configurations in many gaming and power-user PCs, as well as some ultraportable laptops. Such systems have a small, discrete SSD to hold the operating system and frequently used data, augmented by a more capacious conventional hard drive for less frequently accessed data and large collections of documents and digital media.

Current hybrid drive designs, in contrast, deliver both technologies within a single physical unit, and they employ software caching algorithms (rather than relying on the user's brain) to decide which data belongs on the SSD portion and what goes on the driveís platters.

These caching algorithms reside in the hybrid drive's firmware, not the device driver. To the computerís operating system, a hybrid drive appears as a single unit with the SSD portion acting strictly as a large cache. The cache is nonvolatile, so the data doesn't disappear when power is absent.

siljy.datasoft

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Re: Working Of SSHD:--------
« Reply #1 on: January 15, 2015, 10:33:58 PM »
                              How SSH Works
                     ____________________

When you connect through SSH, you will be dropped into a shell session, which is a text-based interface where you can interact with your server. For the duration of your SSH session, any commands that you type into your local terminal are sent through an encrypted SSH tunnel and executed on your server.

The SSH connection is implemented using a client-server model. This means that for an SSH connection to be established, the remote machine must be running a piece of software called an SSH daemon. This software listens for connections on a specific network port, authenticates connection requests, and spawns the appropriate environment if the user provides the correct credentials.

The user's computer must have an SSH client. This is a piece of software that knows how to communicate using the SSH protocol and can be given information about the remote host to connect to, the username to use, and the credentials that should be passed to authenticate. The client can also specify certain details about the connection type they would like to establish.

thanks

nidhinpereira

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Re: Working Of SSHD:--------
« Reply #2 on: January 19, 2015, 10:13:57 PM »
hello,
SSH is a secure protocol used as the primary means of connecting to Linux servers remotely. It provides a text-based interface by spawning a remote shell. After connecting, all commands you type in your local terminal are sent to the remote server and executed there.

In this cheat sheet-style guide, we will cover some common ways of connecting with SSH to achieve your objectives. This can be used as a quick reference when you need to know how to do connect to or configure your server in different ways.
SSH Overview

The most common way of connecting to a remote Linux server is through SSH. SSH stands for Secure Shell and provides a safe and secure way of executing commands, making changes, and configuring services remotely. When you connect through SSH, you log in using an account that exists on the remote server.

When you connect through SSH, you will be dropped into a shell session, which is a text-based interface where you can interact with your server. For the duration of your SSH session, any commands that you type into your local terminal are sent through an encrypted SSH tunnel and executed on your server.

The SSH connection is implemented using a client-server model. This means that for an SSH connection to be established, the remote machine must be running a piece of software called an SSH daemon. This software listens for connections on a specific network port, authenticates connection requests, and spawns the appropriate environment if the user provides the correct credentials.

The user's computer must have an SSH client. This is a piece of software that knows how to communicate using the SSH protocol and can be given information about the remote host to connect to, the username to use, and the credentials that should be passed to authenticate. The client can also specify certain details about the connection type they would like to establish.

When you connect through SSH, you will be dropped into a shell session, which is a text-based interface where you can interact with your server. For the duration of your SSH session, any commands that you type into your local terminal are sent through an encrypted SSH tunnel and executed on your server.

The SSH connection is implemented using a client-server model. This means that for an SSH connection to be established, the remote machine must be running a piece of software called an SSH daemon. This software listens for connections on a specific network port, authenticates connection requests, and spawns the appropriate environment if the user provides the correct credentials.

The user's computer must have an SSH client. This is a piece of software that knows how to communicate using the SSH protocol and can be given information about the remote host to connect to, the username to use, and the credentials that should be passed to authenticate. The client can also specify certain details about the connection type they would like to establish.
How SSH Authenticates Users

Clients generally authenticate either using passwords (less secure and not recommended) or SSH keys, which are very secure.

Password logins are encrypted and are easy to understand for new users. However, automated bots and malicious users will often repeatedly try to authenticate to accounts that allow password-based logins, which can lead to security compromises. For this reason, we recommend always setting up SSH-based authentication for most configurations.

SSH keys are a matching set of cryptographic keys which can be used for authentication. Each set contains a public and a private key. The public key can be shared freely without concern, while the private key must be vigilantly guarded and never exposed to anyone.

To authenticate using SSH keys, a user must have an SSH key pair on their local computer. On the remote server, the public key must be copied to a file within the user's home directory at ~/.ssh/authorized_keys. This file contains a list of public keys, one-per-line, that are authorized to log into this account.

When a client connects to the host, wishing to use SSH key authentication, it will inform the server of this intent and will tell the server which public key to use. The server then check its authorized_keys file for the public key, generate a random string and encrypts it using the public key. This encrypted message can only be decrypted with the associated private key. The server will send this encrypted message to the client to test whether they actually have the associated private key.

Upon receipt of this message, the client will decrypt it using the private key and combine the random string that is revealed with a previously negotiated session ID. It then generates an MD5 hash of this value and transmits it back to the server. The server already had the original message and the session ID, so it can compare an MD5 hash generated by those values and determine that the client must have the private key.

Now that you know how SSH works, we can begin to discuss some examples to demonstrate different ways of working with SSH
Generating and Working with SSH Keys

This section will cover how to generate SSH keys on a client machine and distribute the public key to servers where they should be used. This is a good section to start with if you have not previously generated keys due to the increased security that it allows for future connections.
Generating an SSH Key Pair

Generating a new SSH public and private key pair on your local computer is the first step towards authenticating with a remote server without a password. Unless there is a good reason not to, you should always authenticate using SSH keys.

A number cryptographic algorithms can be used to generate SSH keys, including RSA, DSA, and ECDSA. RSA keys are generally preferred and are the default key type.

To generate an RSA key pair on your local computer, type:  ssh-keygen

santhoshidatasoft

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Re: Working Of SSHD:--------
« Reply #3 on: October 07, 2015, 02:02:38 AM »
An SSD can read and write data many times faster than the best mechanical hard drive. On the downside, flash memory is many times more expensive than the innards of a typical hard drive, so manufacturers have limited their SSD capacities to hit reasonable price points: A 128GB SSD costs about $130, and for that same price tag, you can buy a 3.5-inch desktop hard drive that delivers 2TB of storage, or a 2.5-inch laptop drive that provides 1TB of storage.